Vision testing is normally carried out today either through observation of vision testing charts or through professional evaluation including imaging of the inside of the eye and other advanced diagnostic tools. Professional evaluation is effective in analyzing many vision disorders, but is expensive and may not be available in rural and remote areas. Observation of vision testing charts is effective, but is bulky and cumbersome as the charts are normally mounted on a wall and the test subject must observe them from some distance. While limited, use of vision testing charts and professional evaluations are effective for many common vision disorders such as focusing disorders. However, there are some vision diseases, such as diabetic retinopathy, age-related macular degeneration, and other vision diseases where ongoing monitoring of vision is critically important. Such diseases may become active at specific times and, if not treated, could result in irrecoverable vision loss or even blindness.
Consequently, a small and low-cost device that allows patients suffering from these diseases to conveniently monitor their vision is desirable. Techniques that help to ensure such a system operates properly so that it provides dependable test results are highly desirable. And additional techniques such as vision aids that help a patient in their daily life; electronic magnifier functions; auxiliary imaging and display systems; techniques to ensure the patient taking a test is the properly identified and is actively engaged; and other techniques to ensure accurate testing are also desirable.